Circuit Description
The speed sensor for skid control computer assembly detects the wheel speed and sends the appropriate signals to the skid control computer assembly. The skid control computer assembly converts these signals into a 4-pulse signal and outputs it to the combination meter. It is then transmitted to the ECM. The ECM determines the vehicle speed.
Wheel speed sensors on each wheel deliver an input signal to Vehicle Skid Control (VSC) Electronic Control Unit (ECU). VSC ECU converts input signals from wheel speed sensors to a 4-pulse signal and outputs signal to the combination meter. After this signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter, the signal then sent to ECM. ECM determines vehicle speed based on the frequency of these pulse signals. DTC is set when ECM detects the following conditions simultaneously for 500 times (2 trip detection logic):
- No SP1 (speed sensor) signal while ECM detects SP2 (No. 2 speed sensor) signal.
- Vehicle speed is 6 mph or more for 4 seconds.
- Park/neutral position switch is OFF (Except P and N position).
- Transfer case shift position is except N position (4WD).
Possible causes are:
- Vehicle speed circuit is open or shorted between instrument cluster and ECM.
- Defective combination meter (instrument cluster).
- Defective skid control computer.
- Defective speed sensor.
- Defective ECM.